1. Field of the Invention
This invention relates to organic materials which are particularly useful in the photographic field. In one of its aspects, this invention relates to polymerizable compounds which can be used to form polymers. These polymers, in turn, can be incorporated into photographic materials to obtain a desirable combination of properties. In another of its aspects, this invention relates to photographic elements comprising these polymers.
2. Description of the Prior Art
Due to its good dispersing property and excellent protective colloid properties, gelatin has been used as a binding agent in layers of radiation sensitive elements for many years. Gelatin, however, is susceptible to dimensional change when subjected to varying environmental conditions, e.g., temperature and humidity. Many natural and synthetic polymeric materials such as vinyl polymers, have been proposed as substitutes for gelatin. However, use of these polymers in layers of elements, particularly photographic elements, often adversely affects layer hardness, resistance to abrasion and adhesion to film supports.
These problems are resolved in large measure with the polymers disclosed in U.S. Pat. Nos. 3,459,790 issued Aug. 5, 1969; 3,488,708 issued Jan. 6, 1970; 3,554,987 issued Jan. 12, 1971; and 3,658,878 issued Apr. 25, 1972, all to Smith. These patents relate to film-forming, addition polymers containing at least about 0.1 percent, by weight, of active methylene groups in aliphatic side chains. These polymers can be used as gelatin extenders or substitutes in photographic materials to yield products having dimensional stability and resistance to abrasion. These polymers are capable of crosslinking through the active methylene groups in the side chains. Particularly useful polymers disclosed in the Smith patents are those formed partially or wholly from 2-acetoacetoxyethyl methacrylate or 2-acetoactoxyethyl acrylate.
The compounds disclosed in the Smith patents, particularly 2-acetoacetoxyethyl acrylate and 2-acetoacetoxyethyl methacrylate, copolymerize with other acrylic esters in a fairly random manner resulting in homogeneous copolymers. However, upon copolymerization with vinyl amides, they generally form nonhomogeneous copolymers. Such nonhomogeneous copolymers tend to have low molecular weight fragments of homopolymers of one of the comonomers. When these nonhomogeneous polymers are subjected to many conventional purification techniques, e.g., dialysis, diafiltration or ultrafiltration, to remove impurities, they lose most or all of their capability of crosslinking. The resulting polymers are then no longer useful as gelatin substitutes in photographic materials.
It is well known in the photographic arts that migration of integral hydrophilic color couplers from one layer to another can be minimized by attaching color couplers to polymers in some way. If these same polymers function as gelatin extenders or replacements, thin emulsion layers are possible. Thin emulsion layers are advantageous in saving storage and coating costs. Lipophilic color coupling copolymers are disclosed, for example, in British Patent specification No. 1,130,098 published Oct. 9, 1968. U.S. Pat. No. 3,926,436 issued Dec. 16, 1975 to Monbaliu et al, discloses hydrophilic color coupling latex polymers made from various acrylamides substituted with sulfonic acids or salts. These polymers, however, lack crosslinking sites that are reactive with conventional gelatin hardeners.
Hence, it is desirable to have water-dispersible, crosslinkable polymers which can act simultaneously as polymeric color couplers, binders and gelatin extenders. It is also desirable that these polymers retain their capability of crosslinking after being subjected to such purification techniques as dialysis, dialfiltration and ultrafiltration.